Automated wheel slide detector

ABSTRACT

A wheel slide detection system including an image capture means to capture an image of a wheel and a processing means to receive said captured image, identify said wheel and analyse the relative position of said wheel to determine whether said wheel is rotating.

FIELD OF THE INVENTION

[0001] The present invention is directed towards a system that is ableto detect when one or more wheels on a train are non-rotating orpartially rotating.

BACKGROUND OF THE INVENTION

[0002] A known problem with trains, which can lead to disastrousresults, is that on occasion whilst the train is travelling one or morewheels of the train do not rotate or rotate only partially. This usuallyoccurs when the brake is applied. As the train travels, the non-rotatingor sliding wheel slides along the rail, which in severe circumstancesmay lead to derailment of the train.

[0003] The brakes may be applied due to human error, for example thebrakes may accidentally be left on by the operator. This happens mostfrequently with hand brakes, in which case some wheels may have a brakeapplied and lock up, while other wheels are rotating freely.Non-rotation of the wheels may also be caused by mechanical failure, forexample failure of the pneumatic brakes, or collapse of the bearingpreventing the wheel from rotating. In any case, failures would affectindividual wheel sets or cars, and it is noted that in long trains thisdoes not affect the ability of the train to travel. The reason fornon-rotation or partial non-rotation may be varied, what is important isthe detection of non-rotation or partial non-rotaton.

[0004] If a wheel is not rotating, such that the wheel slides on therail instead of rolling along it, the sliding wheel may develop a flatspot. The friction between the non-rotating wheel and the rail may causethe wheel to overheat. This in turn can cause the wheel to fracture, anda portion of the wheel may break off. In such cases, the axle of thefractured wheel may then become dislodged, damaged, or fractured,leading to derailment.

[0005] A derailed vehicle can damage infrastructure and rolling stockand also become a safety hazard for rail workers and the public.Non-rotating wheels may also cause other less catastrophic problems. Forexample, the rail head may be damaged, or the braking equipment may bedamaged if non-rotation or partial rotation causes wheel flats which inturn may damage the brake blocks.

[0006] In order to guard against non-rotation or partial non-rotation oftrain wheels, it is currently necessary for a train examiner to standnext to the train as it travels past, and for the train examiner toconduct a visual check of the wheels. This can be referred to as roll-byinspection. It is vital that non-rotating wheels are detected during thetime of inspection, as this is the only time that they can be checked.However, this method is not satisfactory, as a train examiner oftenfails to detect a wheel that does not rotate. This solution is alsoprone to human error, whether through inattentiveness, tiredness, poorvisibility, boredom or any other reason.

OBJECT OF THE INVENTION

[0007] It is therefore an object of the present invention to provide animproved system, for detection of non-rotating or partially rotatingwheels on a train, which is not prone to human errors.

SUMMARY OF THE INVENTION

[0008] With the above object in mind, the present invention provides inone aspect a wheel slide detection system including:

[0009] an image capture means to capture an image of a wheel; and

[0010] a processing means to receive the captured image, identify thewheel and analyse the relative position of the wheel to determinewhether the wheel. Is rotating.

[0011] Preferably a plurality of image capture means will be included,and also a plurality of images will be captured to enable relativecomparison between each of the images.

[0012] In preferred arrangements the system would also include a triggermeans to activate the system as a vehicle approaches, for exampleswitch(es) and/or microprocessor generated electronic impuls(es), andalso an illumination means to assist in the capturing of images.

[0013] In further preferred arrangements the image capture means uses aslow shutter or time lapse technique, thus, advantageously rotation,partial rotation or non-rotation of the wheel can be determined from asingle image.

[0014] The system may also calculate the diameter of the wheel so as toassist in determining whether partial rotation of the wheel isoccurring.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] It will be convenient to further describe the invention byreference to the accompanying drawings that illustrate possibleembodiments of the invention.

[0016] Other embodiments of the invention are possible and consequentlythe particularity of the accompanying drawings is not to be understoodas superceding the generality of the preceding description of theinvention.

[0017]FIG. 1 shows the basic arrangement of the present invention.

[0018]FIG. 2 shows a possible process arrangement of the presentinvention.

[0019]FIG. 3 shows an example for determining wheel rotation.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The system of the present invention has been adapted to detectnon-rotation or partial non-rotation of any of the wheels of a train inmotion. As the system is designed to be automated, ft may be located atany point along a track. In the preferred arrangement, the system mayinclude at least one activation means or trigger. This activation meansmay take the form of proximity switches, lasers, optical sensors or thelike, adapted to locate the moving train or wheels. In a simplearrangement, the trigger may simply be a switch located on the track andis activated by the passing of the train. Activation of the triggertells the system that a train is approaching and that image capturingshould commence.

[0021] The usual configuration of a train is that the wheels come in awheel set, such that each set consists of two wheels, connected with apermanently fixed axle. Most wheel sets are designed to ensure that bothwheels rotate at the same time and at the same rate. If a wheel on oneside of the wheel set, i.e., one side of the train, is not rotating,then the other wheel of the wheel set is not rotating either.Accordingly, it is only necessary for the system of the presentinvention to be located on one side of the track if the wheel set isdesigned with a fixed axle that does not rotate. However, in somecircumstances it may be desirable to locate the system on both sides ofthe track. This would allow the system to check the results of one sideagainst the other side, or alternatively allows for inbuilt redundancyin the case of breakdowns or repairs. This would also enable the systemto check for non-rotating or partially rotating wheels if the wheel setis designed in such a way that the wheels on the wheel set do not rotateat the same time.

[0022] In preferred arrangements the system may be directed to analysisof a single image taken by a single camera using a time lapse or slowshutter technique, whereby the camera's shutter is open over a prolongedperiod of time so that the trajectory of the marker or component isvisible in the single image. The trajectory of the feature, marker orcomponent will be seen as a single straight line if the wheel is notrotating in the case of a time lapse image, the camera starts to takethe image as soon as the trigger means is activated. The camera shutterremains open until the wheel travels a sufficient distance to enable thecamera to capture the trajectory of the marker on the wheel on a singleimage. The length of the trajectory on the image must be longer than thelength of the object being traced, the object being the marker,component or feature on the wheel. The camera shutter then closes andmay start to take an image of the next wheel. The image of the previouswheel is then analysed by using edge definition or other techniques todetermine if the trajectory indicates a non-rotating wheel (i.e. If thetrajectory is a relatively straight line on the horizontal plane).

[0023] Alternatively, the system includes a plurality of image capturemeans such as a digital camera. These cameras are designed to capturepictures of the wheels of the trains, and may be fitted with automatediris control mechanisms, if required, to control the image quality,depending on the lighting conditions. Ideally, the camera should becalibrated to achieve high accuracy measurements. The images captured bythe cameras would then be passed to the processing unit for analysis.

[0024] Depending on the location of the system, it may be preferable toinclude a lighting system. Ideally this lighting system would also beactivated at the same time an oncoming train activates a trigger, or atthe same time as the picture is taken by the camera. The number andlocation of the lights required may be dependent on the natural ambientlight, and in a preferred arrangement, the processing unit will assessthe lighting required based on the current ambient light and thenilluminate the necessary number of lights.

[0025] The processing unit receives the captured images from the camerasand assesses whether the wheels are rotating. An image of each-wheel istaken by the camera in a precise manner by using sensor-activated ormicroprocessor-activated triggering. A plurality of consecutive imagesis taken of the same wheel. The images are taken by one or more cameras.The video image processing establishes the center of the wheel bydetecting the edges of the wheel and establishing the wheel's dimension.This step is important, as it provides the reference around which therotation, or non-rotation, or partial rotation of the wheel is detected.The video image processing algorithm chooses a particular visible orelectronically encoded feature or marker on each wheel as a referencefor establishing rotation. The feature or marker is programmed into thevideo image processing algorithm. The video image processing algorithmcompares the location of the feature or marker on consecutive images ofthe same wheel. The system may then assess the rotation of a wheel usingby calculating the angle of the rotation of the wheel. In a basicconfiguration, the system may merely determine whether there has beenany movement of the wheel, opposed to determining the angle of rotation.However, in such an arrangement the system would be unable to determinewhether partial rotation or full rotation was present.

[0026] The plurality of cameras may be used to take a plurality ofimages of each wheel as the train passes. In an alternative arrangement,in some circumstances it may be possible to use a single camera tocapture consecutive images of the wheel in such a way that it wouldstill be able to show any relative motion of the wheel.

[0027] The system may analyse the captured images using image processingsoftware such as MATLAB to determine whether a wheel is rotating byfinding the location of a fixed visual or electronic feature or markeron the wheel and then calculating the angle of rotation of the wheel byfollowing the path of travel of this feature or marker. The system maybe adapted to analyse a distinctive component on the wheel, such as abolt, or may be adapted to locate and track a specially applied featureor marker added to the wheel. The feature or marker could be of anysize, shape, colour or pattern, and may also be mechanical orelectronic. What is required, is that the component, feature, or marker,whether a part of the wheel, or added to the wheel is able to bedetected and tracked by the system.

[0028] Successful detecting of non-rotating or partially rotating wheelsdepends on identifying the centre of the wheel, which can be derived byanalysing the image. The center of the wheel can be derived by edgedetection algorithms that find the outer edges of the wheel or of anyother round component of the wheel, such as an end cap, or by findingthe end cap bolt group whereby each bolt is located at an equal distancefrom the center of the wheel. Other features or components of the wheelmay be used in certain circumstances to establish the location of thecenter of the wheel. Furthermore, the markers or permanent features haveto be identified. At least two images are taken of each wheel, as atleast two images are required for detection. The first image will showthe location of the wheel centre and the markers, or any otherdistinctive features, on the wheel. The second image will then show thelocation of the wheel centre and the markers. If the wheel is rotating,the position of the markers in the first and second images will bedifferent.

[0029] For example, if we consider an example using end cap bolts, whichare distinctive features on the wheel as shown in FIG. 3, we are able tocheck for rotation. The end cap bolts 18 are fixed to the axle 19 andare visible from either side of the train. The bolts 18 are affixed in acircular arrangement around the centre 20 of the wheel 16 usually 1200°apart in the case of 3 end cap bolts. The camera takes two images A, Bin a known period of time. The first image A is used to locate thecentre 20 of the wheel 16 and the initial location of the end cap bolts18. The second image B is used to find the location of the centre 20 ofthe wheel 16 and the bolts 18 after a known period of time. In thisexample, the second picture B is taken at a time when the bolts 18 willtravel less than 120°, so that one bolt does not overlay another bolt ona second image. Each bolt may be identified by its unique feature, suchas as shape and size. However, there is no need to identify each bolt ifthe travel is less than 1200, as this means that one bolt will notoverlay any other bolt in the subsequent image. By comparing thelocation of the bolts on the first and second images, the angle ofrotation of the bolts in this example may be established. This angle ofrotation is compared with the expected angle of rotation, assuming weare able to determine the radius R of the wheel. The radius isdetermined by finding the center of each wheel and referencing it to thetop of the rail. The expected angle of rotation may be determined byusing the following equation:

Angle of wheel rotation=(D/R)×(360/2×π

[0030] Where

[0031] D=Distance traveled by wheel

[0032] R=Radius (of wheel)

[0033] π=3.14159 (mathematical constant)

[0034] The actual angle of rotation may be compared to the expectedangle of rotation. If the actual angle is less than the expected anglethen the wheel is not rotating or is only partially rotating.

[0035] In the preferred arrangement the system uses the radius of thewheel to calculate the anticipated rotation of the fixed components,features or markers and to compare it with the actual rotation. In thisway, the system is able to detect for partial rotation. Whilst partialrotation may not be a significant problem in terms of train safety, itdoes have repercussions in terms of maintenance and replacement costs ofcomponents such as brake pads. Partial rotation may also damage thewheels.

[0036] Should a non-rotating, or partially rotating wheel be detected,the system should provide a warning to the operator to this effect. Thewarning may be sent by radio or any other available type of transmissionto the train driver or any other responsible person. The preferred meansof warning the train driver is by sending a warning message over theradio, as this is the most immediate. In the alternative, orconcurrently, a warning message may also be sent to train control. It isenvisaged that this warning will also be sent by radio or LAN, althoughany other method of communication may also be used. Depending onarrangements in place, the warning message may also be sent by anycommunication means to a computer, telephone or any other recipient ordevice.

[0037] The system may be configured using a combination of hardware andsoftware as shown in FIGS. 1 and 2. One or more triggering means 5, 6may be located adjacent the track 1, together with cameras 3 and lights4. The data from these devices may then be transferred to a processingor main unit 7 which may be located adjacent the track 1 or in alocation remote from the track. The main unit 7 would be configured tomonitor the trigger devices 5, 6 located adjacent the track 1. When thetrigger 5, 6 is activated, a signal is sent to the main unit 7 whichthen activates the lighting 4 if necessary and prepares the cameras 3 tocapture the images.

[0038] Data from the cameras 3 will then be passed to the main unit 7together with any references from the triggering devices 5, 6 or anyother devices that can be used to reference the pictures. Similarly, thecaptured images are analysed and compared to determine whether the wheelis rotating.

[0039] If the system detects that the wheel is rotating, then the nextwheel or axle is considered. Should the system determine that the wheelis not rotating, or in some circumstances only partially rotating, thenan alarm or alert may be sounded.

[0040] Ideally when a non-rotating or partially rotating wheel isdetected, the system will identify which wheel is non-rotating orpartially rotating and forward this information to the desiredrecipients. The system would then also check the next wheel.

[0041] The software controlling the system may be installed on the mainunit 7. The main unit 7 can include a central processing unit, a digitalsignal processor, video capture cards, trigger control software, andimage processing software. On startup or following processing of aprevious wheel, the main unit 7 resets the system variables and waitsfor the trigger to be activated 8. If the trigger 5, 6 is activated, asignal is sent to the main unit 7, the main unit 7 then activates theprocessing unit 9, and as necessary turns on the lighting 4 and datacapture means 2, 3.

[0042] The system then captures 10 the video data with reference to thetriggers. The main unit 7 then analyses 11 this data comparing it withexpected results so as to determine whether the wheel is rotating 12. Ifthe wheel is rotating, then the system considers the next axle 13 andrepeats the process of capturing the image 10 and analysing the data 11.If the wheel is not rotating or partially rotating then an alarm istransmitted 14 before the system then considers the next wheel 15. Onceall the wheels have been analysed, the system is then able to reset andawait a further trigger.

[0043] The present invention discloses an automated wheel slidedetection system. This system includes computer hardware and softwarethat may be installed at any location near the track, and uses imageassessment to detect whether a wheel is rotating.

[0044] As soon as a non-rotating or partially rotating wheel isdetected, the system preferably issues a warning (audio and/or visual)and may send a warning message to a recipient (for example, to the traindriver or to the train controller). This message can be sent by anyconvenient means (such as radio, SMS, Internet). The system ideallyidentifies the location of the sliding wheel either by reference to theaxle or vehicle. The train can then be stopped, and appropriate actioncan be taken by the railway operator.

[0045] The wheel slide detection system can be fully automatic andenables every wheel that goes past to be checked. As a result, wheelsthat do not rotate and may cause an accident are flagged as soon as theyhave passed the wheel slide detector and a warning is issued to asuitable recipient. Because of the system's automation feature, it canbe installed anywhere along the track. Automation also makes it morereliable and consistent than employing a human train examiner.

[0046] Whilst the system of the present invention has been summarisedand explained it will be appreciated by those skilled in the art thatmany widely varying embodiments and applications are within the teachingand, scope of the present invention, and that the examples presentedherein are by way of illustration only and should not be construed aslimiting the scope of this invention.

1. A wheel slide detection system including: an image capture means to capture an image of a wheel; and a processing means to receive said captured image, identify said wheel and analyse the relative position of said wheel to determine whether said wheel is rotating.
 2. A system as claimed in claim 1, wherein a plurality of image capture means are included.
 3. A system as claimed in claim 1 or 2, wherein a plurality of images are captured by said image capture means to enable relative comparison between each said image.
 4. A system as claimed in claim 3, wherein the comparison is made between consecutive captured images.
 5. A system as claimed in any one of the preceding claims, further including a trigger means to activate said image capture means.
 6. A system as claimed in claim 5, wherein said trigger means is a switch or an electronic impulse generated by a microprocessor.
 7. A system as claimed in any one of the preceding claims further including at least one additional trigger means to provide at least one reference point for said processing means.
 8. A system as claimed in any one of the preceding claims wherein each said image capture means is a camera.
 9. A system as claimed in claim 8, wherein said camera includes automated iris control mechanisms adapted to adjust to varying lighting conditions.
 10. A system as claimed in any one of the preceding claims further including a lighting means to illuminate said wheel.
 11. A system as claimed in claim 10, further including a lighting control means to adjust the illumination provided by said lighting means dependent on ambient conditions.
 12. A system as claimed in any one of the preceding claims, wherein to determine whether said wheel is rotating, said processing means identifies a fixed component, feature or marker on said wheel, and analyses the movement of said fixed component or feature to determine whether said wheel is rotating.
 13. A system as claimed in claim 12, wherein at least two images are captured. by said image capture means, and said processing means compares the relative position of said component, marker or feature in each said image to determine rotation.
 14. A system as claimed in claim 12 or 13, wherein the degree of rotation determined by said processing means is compared with expected rotation of said wheel to determine whether said wheel is partially or fully rotating.
 15. A system as claimed in claim 14, wherein the expected angle (f rotation is determined by (D/R)×(360/2xπ) where D equals distance traveled by said wheel, R equals radius of said wheel, and π is a mathematical constant.
 16. A system as claimed in claim 1, wherein the image capture means uses a slow shutter or time lapse technique.
 17. A system as claimed claim 16, wherein to determine whether said wheel is rotating, said processing means identifies a fixed component, feature or marker on said wheel, and analyses the movement of said fixed component or feature to determine whether said wheel is rotating.
 18. A system as claimed in any one of the preceding claims wherein if said processing means determines said wheel is not rotating, or is partially rotating, an alert or warning message is sent to at least one predetermined recipient. 